Sophisticated instrumentation used to monitor operating conditions in the harsh environment of a turbomachine is complex and expensive. Undetected fatigue failure of such instrumentation can not only involve costly shutdowns for repair and/or replacement of the instrumentation, but it can also result in damage to the machine itself. For example, inlet rakes are used to monitor temperature, pressure, velocity and/or other parameters of air entering the turbine inlet and flowing across the rake. They are typically mounted to the inlet sidewall in cantilevered fashion, with the sensor beam or tube extending into the flowpath. Conditions within the flowpath can cause vibrations that may excite the natural or resonance frequency of the beam, causing catastrophic failure of the beam, which may then also result in severe damage to the downstream turbine blades or other flowpath components.
There is a need, therefore, to devise a way to monitor and detect a stress/strain level in a component (a turbine inlet rake in the exemplary embodiment) that exceeds a predetermined stress/strain level below that at which the component will fail in fatigue, thus providing the user or operator with a clear indication or early warning that the component is at risk.